Thermal reversible, proteins

The property of thermal, reversible gelation is obtained by the addition of water-soluble proteins and protein degradation products to an aqueous solution of poly (vinyl alcohol) 2). Protein products such as albumin, gelatin, glue, a-amino acids, and their condensation products—diketopiperazines—may be used. A typical formulation for the preparation of a thermally reversible gel is ... 

These thermal analysis studies serve to establish a direct relationship between a heat-induced AR method and the reversal of formalin-induced intra- and intermolecular protein cross-links.10 2831 Further, while formalin-treatment provides thermal stability to RNase A, this stabilization is not sufficient to prevent thermally induced protein denaturation at temperatures (>100°C) typically used in heat-induced AR methods.32 34 The implications of this finding for the mechanism of AR will be discussed further in Section 15.6. 

A Thermally Reversible, Water-Soluble, Activated Polymer for Protein Coiyugation... 

Thermally reversible gels based on NIPA polymers and copolymers of N,N-diethylacrylamide and sodium methacrylate collapsed abruptly upon heating at 33 °C and 55 °C, respectively [69]. These materials could be used in separation processes. Collapsed gel samples were added to a solution which contained a protein or other macromolecule and various small solutes. The gel... 

Cole C-A, Schreiner SM, Priest JH, Monji N, Hoffman AS. Al-isopropylacrylamide and Al-acryloxysuccinimide copolymer a thermally reversible, water-soluble, activated polymer for protein conjugation. In Russo P, ed. Reversible Polymeric Gels and Related Systems. Washington, DC American Chemical Society, 1987 245-254. 

Fig. 3. Differential scanning calorimetry scans of biomembrane transitions, all obtained with 50% ethylene glycol/water as solvent. (A) A. laidlawii membranes from cells grown in tryptose medium at 37 C (B) lysodeikticus membranes from cells grown in brain heart infusion at 37 C (C) JE. coli K12W945 whole cells grown in minimal salts with glucose at 20 C (D) the same cells as in (C), but scanned after thermal protein (E) rat liver microsomes (F) rat liver In all cases a lower temperature reversible lipid transition is followed by a higher temperature irreversible protein peak. The protein denaturation peaks are featureless in (A), (E), and (F), but show fine structure in (B), (C), and (D). Unlike other organisms, coli after heating shows two lipid transitions and residual reversible protein denaturation, as seen in (D).

Water-soluble proteins as natural biopolymers are irreplaceable components in various technologies used in the development of new functional products in food, cosmetic, pharmaceutical medical application and so on. Gelatin occupies an important place in this case due to its unique capability to thermal reversible gel formation in the bulk as well as at liquid interfaces [1-3]. 

Kawaguchi H, Fujimoto K, Mizuhara Y. Hydrogel microspheres III. Temperature-dependent adsorption of proteins on poly-Al-isopropylacrylamide hydrogel microspheres. Colloid Polym. Sci. 1992 270 53-57. Hoffman S, Afrassiabi A, Dong LS. Thermally reversible hydrogels II. Delivery and selective removal of substances from aqneons solutions. J. Control. Release 1986 4 213-222. 

Thermodynamic parameters can be defined only for a reversible process. The midpoint corresponding to a thermally reversible folding-unfolding transition of a protein is defined by the temperature of transition, (i.e., the temperature at which the apparent transition constant K is equal to 1, and AG, the variation of free energy, is nul under conditions where a two-state approximation is valuable). Under these conditions is equal to AH/AS and AG is equal to AH(1 — T/T ). The different parameters are defined in Chapter 6 however, it is noted here that Privalov and Khechinaschvili (1974) have shown that AH is a linear function of temperature for a number... 

In summary, formalin-treated does not significantly perturb the native structure of RNase A at room temperature. It also serves to stabilize the protein against the denaturing effects of heating as revealed by the increase in the denaturation temperature of the protein. However, formalin-treatment does not stabilize RNase A sufficiently to prevent the thermal denaturation of the protein at temperatures used in heat-induced AR methods as shown by both DSC and CD spectropolarimetry. This denaturation likely arrises from the heat-induced reversal of formaldehyde cross-links and adducts, as shown in Figure 15.4 of Section 15.4. Further, cooling formalin-treated RNase A that had been heated to 95°C for 10 min does not result in the restoration of the native structure of the protein, particularly in regard to protein tertiary structure. 

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